Nickel electrodes for alkaline storage batteries are classified into sintered electrodes and nonsintered electrodes. A sintered nickel electrode using a sintered substance of a metal as a conductive substrate (collector) has a disadvantage of a small packing amount of an active material, namely, low energy density, because of low porosity of the sintered substance. Therefore, a nonsintered nickel electrode using a foamed metal with high porosity as a conductive substrate for packing a large amount of active material has recently become noticeable.
However, a nickel electrode, whether it may be sintered or nonsintered, has a problem that the utilization of an active material is so low that desired energy density and desired discharge capacity cannot be attained because nickel hydroxide has poor charge acceptance (charge efficiency).
For improving the charge acceptance of nickel hydroxide, a method for allowing cobalt (bivalent cobalt) to be included in nickel hydroxide as a solid-solution element is known (see Japanese Laid-Open Patent Publication No. 3-78965).
As a result of examination made by the present inventors, however, it has been found that the charge acceptance of nickel hydroxide cannot be sufficiently improved by the conventional method.
The present invention was devised to overcome the problem of the conventional method, and an object is providing a nonsintered nickel electrode exhibiting good charge acceptance sufficient for attaining large discharge capacity and high energy density.